It is desired to develop a system to support short range wireless data communication to inexpensive endpoints. Radio Frequency IDentification (RFID) systems are radio communication systems that communicate between a radio transceiver, called an Interrogator, and a number of inexpensive devices called Tags. RFID technology may be appropriate to consider in the development of such a system. In RFID systems, the Interrogator communicates to the Tags using modulated radio signals, and the Tags respond with modulated radio signals. Typically, communications from the Interrogator to the Tag utilize amplitude modulated radio signals, which are easily demodulated. For communications from the Tag to the Interrogator, Modulated BackScatter (MBS) is a commonly used technique. In MBS, the Interrogator transmits a Continuous-Wave (CW) radio signal to the Tag. The Tag then modulates the CW signal using MBS where the antenna is electrically switched, by the Tag's modulating signal, from being an absorber of RF radiation to being a reflector of RF radiation; thereby encoding data from the Tag onto the CW radio signal. The Interrogator demodulates the incoming modulated radio signal and decodes the Tag's data message. For Tag to Interrogator MBS communications, prior art maintains the use of Frequency Shift Keying (FSK) modulation and Phase Shift Keying (PSK) techniques for communications.
What is needed is a communications system that will allow short range wireless data communication to a number of inexpensive endpoints. As an example, consider the communication of sensor data within a space where a large amount of electronic equipment is present. Such a situation could occur within the control room of an industrial process, within a compartment of a naval vessel, within a manufacturing environment, within a military vehicle such as a tank, within the electronics on board an aircraft, etc. In such applications there may be as many as 1,000 sensors to be monitored. Present technology supports the use of sensors connected via wires to central communication points which can be very expensive to install. Current technology also supports the use of wireless Local Area Networks (WLANs) to interconnect the endpoints to a central communication point, however they are expensive.
Thus, there is a continuing need for an inexpensive wireless data network which will allow data communications to a large number of inexpensive devices, such as sensors.